160 WHAT DOES MAN LIVE UPON? 



of the Englishman, Hales, and the German, Schiibler, it 

 seems to follow that .plants consume a much greater quan- 

 tity of water than falls in the shape of rain. A sun-flower 

 consumes daily 22 ounces of water; consequently, if every 

 plant occupies four square feet of the soil, the plants of one 

 acre would require 1,826,706 Ibs. in the four summer 

 months. But the ground between them is overgrown with 

 grass and weeds, and these consume water, which may 

 again be estimated at about the same quantity. Therefore, 

 an acre of land, planted with sunflowers, would require 

 altogether more than three million pounds of water. 



By similar calculations it is found, that an acre planted 

 with cabbages, requires more than five million pounds of 

 water ; an orchard stocked with dwarf apple-trees, an equal 

 quantity ; and an acre planted with hops, as much as six 

 or seven millions of pounds. 



The experiments on which these calculations are founded, 

 were made in England, where, during the summer months, 

 at most not more than 2,325,000 Ibs. of rain fall on an 

 acre of land. But it would be a great error to suppose 

 that all this rain-water is available to the plant. A large 

 portion is diffused by evaporation through the air, and a 

 yet greater portion runs away, and is carried to the sea by 

 springs, brooks and rivers. We do not at present possess 

 any measurements and calculations sufficiently accurate to 

 enable us to determine this latter quantity. It is, however, 

 very remarkable, that as in the course of centuries the 

 methods of determination have been gradually deve- 

 loped and improved, and the observations become more 

 accurate, it has turned out that these quantities of 

 water were formerly estimated at much below the real 

 amount. The older natural philosophers assumed that 

 one- sixth of the water falling as rain was carried away 



